Polyalkylene oxides having hindered ester-based biodegradable linkers

ABSTRACT

The present invention provides polymeric delivery systems including hindered ester moieties. Methods of making the polymeric delivery systems and methods of treating mammals using the same are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a continuation of PCT/US2007/078593 filed Sep. 15, 2007, which claims the benefit of priority from U.S. Provisional Patent Application Ser. No. 60/844,942 filed Sep. 15, 2006, the contents of each of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to improved activated polymers such as polyalkylene oxides. In particular, the invention relates to activated polymers containing hindered ester moieties which improve delivery of certain biologically active moieties including oligonucleotides.

BACKGROUND OF THE INVENTION

Over the years, numerous methods have been proposed for delivering therapeutic agents into body and improving bioavailability of those medicinal agents. One of the attempts is to include such medicinal agents as part of a soluble transport system. Such transport systems can include permanent conjugate-based systems or prodrugs. In particular, polymeric transport systems can improve the solubility and stability of medicinal agents. For example, the conjugation of water-soluble polyalkylene oxides with therapeutic moieties such as proteins and polypeptides is known. See, for example, U.S. Pat. No. 4,179,337 (the '337 patent), the disclosure of which is incorporated herein by reference. The '337 patent discloses that physiologically active polypeptides modified with PEG circulate for extended periods in vivo, and have reduced immunogenicity and antigenicity.

Additional improvements have been also realized. For example, polymer-based drug delivery platform systems containing benzyl elimination systems, trimethyl lock systems, etc. were disclosed by Enzon Pharmaceuticals and Zhao, et al. as a means of releasably delivering proteins, peptides and small molecules. See also Greenwald, et al., J. Med. Chem. Vol. 42, No. 18, 3657-3667; Greenwald, et al., J. Med. Chem. Vol. 47, No. 3, 726-734; Greenwald, et al., J. Med. Chem. Vol. 43, No. 3, 475-487. The contents of each of the foregoing are hereby incorporated herein by reference.

More recently, PEG has been proposed for conjugation with oligonucleotides, especially oligonucleotides that are complementary to a specific target messenger RNA (mRNA) sequence. Generally, nucleic acid sequences complementary to the products of gene transcription (e.g., mRNA) are designated “antisense”, and nucleic acid sequences having the same sequence as the transcript or being produced as the transcript are designated “sense”. See, e.g., Crooke, 1992, Annu. Rev. Pharmacol. Toxicol., 32: 329-376. An antisense oligonucleotide can be selected to hybridize to all or part of a gene, in such a way as to modulate expression of the gate. Transcription factors interact with double-stranded DNA during regulation of transcription.

Oligonucleotides have also found use in among others, diagnostic tests, research reagents e.g. primers in PCR technology and other laboratory procedures. Oligonucleotides can be custom synthesized to contain properties that are tailored to fit a desired use. Thus numerous chemical modifications have been introduced into oligomeric compounds to increase their usefulness in diagnostics, as research reagents and as therapeutic entities.

Although oligonucleotides, especially antisense oligonucleotides show promise as therapeutic agents, they are very susceptible to nucleases and can be rapidly degraded before and after they enter the target cells making unmodified antisense oligonucleotides unsuitable for use in in vivo systems. Because the enzymes responsible for the degradation are found in most tissues, modifications to the oligonucleotides have been made in an attempt to stable the compounds and remedy this problem. The most widely tested modifications have been made to the back bone portion of the oligonucleotide compounds. See generally Uhlmann and Peymann, 1990, Chemical Reviews 90, at pages 545-561 and references cited therein. Among the many different back bones made, only phosphorothioate showed significant antisense activity. See for example, Padmapriya and Agrawal, 1993, Bioorg. & Med. Chem. Lett. 3, 761. While the introduction of sulfur atoms to the back bone slows the enzyme degradation rate, it also increases toxicity at the same time. Another disadvantage of adding sulfur atoms is that it changes the back bone from achiral to chiral and results in 2^(n) diastereomers. This may cause further side effects. Still more disadvantages of present antisense oligonucleotides are that they may carry a negative charge on the phosphate group which inhibits its ability to pass through the mainly lipophilic cell membrane. The longer the compound remains outside the cell, the more degraded it becomes resulting in less active compound arriving at the target. A further disadvantage of present antisense compounds is that oligonucleotides tend to form secondary and high-order solution structures. Once these structures are formed, they become targets of various enzymes, proteins, RNA, and DNA for binding. This results in nonspecific side effects and reduced amounts of active compound binding to mRNA. Other attempts to improve oligonucleotide therapy have included adding a linking moiety and polyethylene glycol. See for example, Kawaguchi, et al., Stability, Specific Binding Activity, and Plasma Concentration in Mice of an Oligodeoxynucleotide Modified at 5′-Terminal with Poly(ethylene glycol), Biol. Pharm. Bull., 18(3) 474-476 (1995), and U.S. Pat. No. 4,904,582. In both of these examples, the modifications involve the use of linking moieties that are permanent in nature in an effort to stabilize the oligonucleotide against degradation and increase cell permeability. However, both of these efforts fail to provide any in vivo efficacy.

To conjugate therapeutic agents such as small molecules and oligonucleotides to polyalkylene oxides, the hydroxyl end-groups of the polymer must first be converted into reactive function groups. This process is frequently referred to as “activation” and the product is called an “activated polyalkylene oxide”. Other polymers are similarly activated.

In spite of the attempts and advances, further improvements in PEG and polymer conjugation technology such as activated polymers have therefore been sought. The present invention addresses this need and others.

SUMMARY OF THE INVENTION

In order to overcome the above problems and improve the technology for drug delivery, there are provided new activated polymers and conjugates made therewith.

In one aspect of the present invention, there are provided compounds of Formula (I):

wherein:

A is a capping group or

R₁ is a substantially non-antigenic water-soluble polymer;

L₁ and L′₁ are independently selected spacers having a free electron pair positioned four to ten atoms from C(═Y₁) or C(═Y′₁), preferably 4 to 8 and most preferably 4 to 5 atoms from C(═Y₁) or C(═Y′₁);

L₂ and L′₂ are independently selected bifunctional linkers;

Y₁ and Y′₁ are independently O, S, or NR₅;

R₂, R′₂, R₃, R′₃ and R₅ are independently selected from among hydrogen, C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₁₉ branched alkyl, C₃₋₈ cycloalkyl, C₁₋₆ substituted alkyl, C₂₋₆ substituted alkenyl, C₂₋₆ substituted alkynyl, C₃₋₈ substituted cycloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, C₁₋₆ heteroalkyl, substituted C₁₋₆ heteroalkyl C₁₋₆ alkoxy, aryloxy, C₁₋₆ heteroalkoxy, heteroaryloxy, C₂₋₆ alkanoyl, arylcarbonyl, C₂₋₆ alkoxycarbonyl, aryloxycarbonyl, C₂₋₆ alkanoyloxy, arylcarbonyloxy, C₂₋₆ substituted alkanoyl, substituted arylcarbonyl, C₂₋₆ substituted alkanoyloxy, substituted aryloxycarbonyl, C₂₋₆ substituted alkanoyloxy and substituted arylcarbonyloxy, or R₂ together with R₃ and R′₂ together with R′₃ independently form a substituted or unsubstituted non-aromatic cyclohydrocarbon containing at least three carbons;

R₄ and R′₄ are independently selected from among OH, leaving groups, targeting groups, diagnostic agents and biologically active moieties; and

(p) and (p′) are independently zero or a positive integer, preferably zero or an integer from about 1 to about 3, more preferably zero or 1,

provided that R₃ is a substituted or unsubstituted hydrocarbon having at least three carbons when R₂ is H, and further provided that L₁ is not the same as C(R₂)(R₃).

In certain preferred embodiments of this aspect of the invention, the substantially non-antigenic polymer is a polyalkylene oxide and is more preferably polyethylene glycol (hereinafter PEG). In other aspects, the PEG is either capped on one terminal with a CH₃ group, i.e. mPEG, while in other embodiments, bis-activated PEGs are provided such as those corresponding to the formula:

Still flier aspects of the invention include methods of making the activated polymers containing the hindered ester, methods of making conjugates, including oligonucleotide conjugates, containing the same as well as methods of treatment based on administering effective amounts of conjugates containing a biologically active moiety to a patient (mammal) in need thereof.

The polymeric delivery systems described herein include novel linkers which can form a releasable bond such as an ester bond between the polymer and biologically active moiety. The polymeric systems are based on a hindered acid structure which is built as part of the polymer, i.e. PEG backbone, and activated as an acid ester such as NHS ester on the polymer. The activated forms can react with an hydroxy or thiol group containing moiety to form a releasable ester bond.

One advantage of the hindered ester-based polymeric transport systems described herein is that the polymeric delivery systems have improved stability. Without being bound by any theories, the ester bond in a sterically hindered environment between the polymer and a moiety such as a leaving group, a biologically active moiety and a targeting group can inhibit the ester linkage from being exposed to basic aqueous medium or enzymes, and thereby stabilizes the covalent linkage. The stability of the polymeric systems allows long-term storage prior to attaching to targeting groups or biologically active moieties, and longer shelf life for the polymeric conjugate containing biologically active moieties. The improved stability increases cost efficiency.

Still further aspects of the invention include methods of making the activated polymers containing the hindered ester, methods of making conjugates, including oligonucleotide conjugates, containing the same as well as methods of treatment based on administering effective amounts of conjugates containing a biologically active moiety to a patient (mammal) in need thereof.

Another advantage of the activated polymers corresponding to the invention is that they are especially well suited for use with oligonucleotides and related antisense or short-interfering RNA (siRNA) compounds. The presence of the hindered ester group in proximity to the oligonucleotide attached thereto provides improved stability and resistance to nuclease degradation. It also helps decrease toxicity and increase binding affinity to mRNA of oligonucleotide compounds. Conjugates made in accordance with the invention provide a means for protecting antisense oligonucleotide compounds against degradation, preventing the formation of high-order structures. Moreover, the polymer conjugates allow the artisan to deliver sufficient amounts of active antisense oligonucleotide compounds to the target.

Another advantage, of the activated polymers containing the hindered esters is that it allows the artisan to more easily conjugate oligonucleotides of choice. There is no need to modify the oligonucleotide or target moiety with the hindered ester before PEGylation. The oligo is taken as is and PEGylated with the activated PEG linker which contains the desired hindered ester protective group thereon.

Yet another advantage of the activated polymers corresponding to the invention is that they are especially well suited for use with oligonucleotides and related antisense compounds. The presence of the hindered ester group in proximity to the oligonucleotide attached thereto provides improved stability and resistance to increase degradation. It also helps decrease toxicity and increase binding affinity to mRNA of oligonucleotide compounds. Conjugates made in accordance with the invention provide a means for protecting antisense oligonucleotide compounds against degradation, preventing the formation of high-order structures. Moreover, the polymer conjugates allow the artisan to deliver sufficient amounts of active antisense oligonucleotide compounds to the target.

Although several aspects of is invention are described with respect to linking with oligonucleotides, it will be appreciated by those of ordinary skill that the activated polymers containing one or more “hindering” groups thereon have a broad utility in the field of polymer conjugation. The activated forms of the polymer can be used to releasably and permanently link polymers such as PEG to proteins, peptides, enzymes, small molecules, etc.

For purposes of the present invention, the terms “a biologically active moiety” and “a residue of a biologically active moiety” shall be understood to mean that portion of a biologically active compound which remains after the biologically active compound has undergone a substitution reaction in which the transport carrier portion has been attached.

Unless otherwise defined, for purposes of the present invention:

the term “alkyl” shall be understood to include straight, branched, substituted, e.g. halo-, alkoxy-, and nitro-C₁₋₁₂ alkyls, C₃₋₈ cycloalkyls or substituted cycloalkyls, etc.;

the term “substituted” shall be understood to include adding or replacing one or more atoms contained within a functional group or compound with one or more different atoms;

the term “substituted alkyls” include carboxyalkyls, aminoalkyls dialkylaminos, hydroxyalkyls and mercaptoalkyls;

the term “substituted cycloalkyls” include moieties such as 4-chlorocyclohexyl; aryls include moieties such as napthyl; substituted aryls include moieties such as 3-bromophenyl; aralkyls include moieties such as toluoyl; heteroalkyls include moieties such as ethylthiophene;

the term “substituted heteroalkyls” include moieties such as 3-methoxy-thiophene; alkoxy includes moieties such as methoxy; and phenoxy includes moieties such as 3-nitrophenoxy;

the term “halo” shall be understood to include fluoro, chloro, iodo and bromo; and

the terms “sufficient amounts” and “effective amounts” for purposes of the present invention shall mean an amount which achieves a therapeutic effect as such effect is understood by those of ordinary skin in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates methods of synthesis described in Examples 1-2.

FIG. 2 schematically illustrates methods of synthesis described in Example 3-11.

FIG. 3 schematically illustrates methods of synthesis described in Example 12.

FIG. 4 schematically illustrates methods of synthesis described in Examples 13-15.

FIG. 5 schematically illustrates methods of synthesis described in Example 16.

DETAILED DESCRIPTION OF THE INVENTION A. Overview

In most aspects of the invention, the polymers included herein are generally described as substantially non-antigenic polymers. Within this genus of polymers, polyalkylene oxides are preferred and polyethylene glycols (PEG's) are most preferred. For purposes of ease of description rather than limitation, the invention is sometimes described using PEG as the prototypical polymer. It should be understood, however, that the scope of the invention is applicable to a wide variety of polymers which can be linear, substantially linear, branched, etc. One of the only requirements is that the polymer contains the means for covalently attaching the desired hindered ester groups described herein and that it can withstand the processing required to transform the resulting intermediate into the activated linker containing polymer and resulting conjugate under the conditions described herein.

In accordance with the foregoing, there are provided compounds of Formula (I):

wherein:

A is a capping group or

R₁ is a substantially non-antigenic water-soluble polymer;

L₁ and L′₁ are independently selected spacers having a free electron pair positioned four to ten atoms from C(═Y₁) or C(═Y′₁), preferably from about 4 to about 8 and most preferably from about 4 to about 5 atoms from C(═Y₁) or C(═Y′₁);

L₂ and L′₂ are independently selected bifunctional linkers;

Y₁ and Y′₁ are independently O, S, or NR₅;

R₂, R′₂, R₃, R′₃ and R₅ are independently selected from along hydrogen, C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₁₉ branched alkyl, C₃₋₈ cycloalkyl, C₁₋₆ substituted alkyl, C₂₋₆ substituted alkenyl, C₂₋₆ substituted alkynyl, C₃₋₈ substituted cycloalkyl, aryl, substituted aryl, heteroaryl substituted heteroaryl, C₁₋₆ heteroalkyl, substituted C₁₋₆ heteroalkyl, C₁₋₆ alkoxy, aryloxy, C₁₋₆ heteroalkoxy, heteroaryloxy, C₂₋₆ alkanoyl, arylcarbonyl, C₂₋₆ alkoxycarbonyl, aryloxycarbonyl, C₂₋₆ alkanoyloxy; arylcarbonyloxy, C₂₋₆ substituted alkanoyl, substituted arylcarbonyl, C₂₋₆ substituted alkanoyloxy, substituted aryloxycarbonyl C₂₋₆ substituted alkanoyloxy and substituted arylcarbonyloxy, or R₂ together with R₃ and R′₂ together with R′₃ independently form a substituted or unsubstituted non-aromatic cyclohydrocarbon containing at least three carbons;

R₄ and R′₄ are independently selected from among OH, leaving groups, targeting groups, diagnostic agents and biologically active moieties; and

(p) and (p′) are independently zero or a positive integer, preferably zero or an integer from about 1 to about 3, more preferably zero or 1;

provided that R₃ is a substituted or unsubstituted hydrocarbon having at least three carbons when R₂ is H, and further provided that L₁ is not the same as C(R₂)(R₃).

In certain preferred embodiments of this aspect of the invention, substantially non-antigenic polymer is a polyalkylene oxide and is more preferably polyethylene glycol (hereinafter PEG). In other aspects, the PEG is either capped on one terminal with a CH₃ group, i.e. mPEG. Oater optional capping groups include H, NH₂, OH, CO₂H, C₁₋₆ alkoxy and C₁₋₆ alkyl. Preferred capping groups include methoxy and methyl.

In other embodiments, bis-activated PEGs are provided such as those corresponding to Formula (II):

Within those aspects of the invention, the substituents contemplated for substitution, where the moieties corresponding to R₂, R′₂, R₃, R′₃ and R₅ are indicated as being possibly substituted can include, for example, acyl, amino, amido, amidine, ara-alkyl, aryl, azido, alkylmercapto, arylmercapto, carbonyl, carboxylate, cyano, ester, ether, formyl, halogen, heteroaryl, heterocycloalkyl, hydroxy, imino, nitro, thiocarbonyl, thioester, thioacetate, thioformate, alkoxy, phosphoryl, phosphonate, phosphinate, silyl, sulfhydryl, sulfate, sulfonate, sulfamoyl, sulfonamide, and sulfonyl.

Preferably, L₁ and L′₁ are independently selected spacers having a free electron pair positioned four to eight atoms from C(═Y₁) or C(═Y′₁); more preferably four to six; and both Y and Y′₁ are O.

In another aspect of the invention, the biological moieties include —OH containing moieties and —SH containing moieties.

In yet another aspect, A can be selected from among H, NH₂, OH, CO₂H, C₁₋₆ alkoxy, and C₁₋₆ alkyls. In some preferred embodiments, A can be methyl ethyl, methoxy, ethoxy, H, and OH. A is more preferably methyl or methoxy.

B. Substantially Non-Antigenic Water-Soluble Polymers

Polymers employed in the polymeric delivery systems described herein are preferably water soluble polymers and substantially non-antigenic such as polyalkylene oxides (PAO's).

In one aspect of the invention, the compounds described herein include a linear, terminally branched or multi-armed polyalkylene oxide. In some preferred embodiments, the polyalkylene oxide includes polyethylene glycol and polypropylene glycol.

The polyalkylene oxide has an average molecular weight from about 2,000 to about 100,000 daltons, preferably from about 5,000 to about 60,000 daltons. In some aspects the polyalkylene oxide can be from about 5,000 to about 25,000, and preferably from about 12,000 to about 20,000 daltons when proteins or oligonucleotides are attached or alternatively from about 20,000 to about 45,000 daltons, and preferably from about 30,000 to about 40,000 daltons when pharmaceutically active compounds (small molecules) are employed in the compounds described herein.

The polyalkylene oxide includes polyethylene glycols and polypropylene glycols. More preferably, the polyalkylene oxide includes polyethylene glycol (PEG). PEG is generally represented by the structure: —O—(CH₂CH₂O)_(n)— where (n) is an integer from about 10 to about 2,300, and is dependent on the number of polymer arms when multi-arm polymers are used. Alternatively, the polyethylene glycol (PEG) residue portion of the invention can be selected from among: —Y₇₁—(CH₂CH₂O)_(n)—CH₂CH₂Y₇₁—, —Y₇₁—(CH₂CH₂O)_(n)—CH₂C(═Y₇₂)—Y₇₁—, —Y₇₁—C(═Y₇₂)—(CH₂)_(a71)—Y₇₃—(CH₂CH₂O)_(n)—CH₂CH₂—Y₇₃—(CH₂)_(a71)—C(═Y₇₂)—Y₇₁—, and —Y₇₁—(CR₇₁R₇₂)_(a72)—Y₇₃—(CH₂)_(b71)—O—(CH₂CH₂O)_(n)—(CH₂)_(b71)—Y₇₃—(CR₇₁R₇₂)_(a72)—Y₇₁—,

wherein:

Y₇₁ and Y₇₃ are independently O, S, SO, SO₂, NR₇₃ or a bond;

Y₇₂ is O, S, or NR₇₄;

R₇₁₋₇₄ are independently the same moieties which can be used for R₂;

(a71), (a72), and (b71) are independently zero or a positive integer, preferably 0-6, and more preferably 1; and

(n) is an integer from about 10 to about 2300.

Branched or U-PEG derivatives are described in U.S. Pat. Nos. 5,643,575, 5,919,455, 6,113,906 and 6,566,506, the disclosure of each of which is incorporated herein by reference. A non-limiting list of such polymers corresponds to polymer systems (i)-(vii) with the following structures:

wherein:

Y₆₁₋₆₂ are independently O, S or NR₆₁;

Y₆₃ is O, NR₆₂, S, SO or SO₂

(w62), (w63) and (w64) are independently 0 or a positive integer;

(w61) is 0 or 1;

mPEG is methoxy PEG

-   -   wherein PEG is previously defined a and a total molecular weight         of the polymer portion is from about 2,000 to about 100,000         daltons; and

R₆₁ and R₆₂ are independently selected from among hydrogen, C₁₋₆ alkyl C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₁₉ branched alkyl, C₃₋₈ cycloalkyl, C₁₋₆ substituted alkyl, C₂₋₆ substituted alkenyl, C₂₋₆ substituted alkynyl, C₃₋₈ substituted cycloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, C₁₋₆ heteroalkyl, substituted C₁₋₆ heteroalkyl C₁₋₆ alkoxy, aryloxy, C₁₋₆ heteroalkoxy, heteroaryloxy, C₂₋₆ alkanoyl, arylcarbonyl, C₂₋₆ alkoxycarbonyl, aryloxycarbonyl, C₂₋₆ alkanoyloxy, arylcarbonyloxy, C₂₋₆ substituted alkanoyl, substitute arylcarbonyl, C₂₋₆ substituted alkanoyloxy, substituted aryloxycarbonyl, C₂₋₆ substituted alkanoyloxy, and substituted and arylcarbonyloxy.

In yet another aspect, the polymers include multi-arm PEG-OH or “star-PEG” products such as those described in NOF Corp. Drug Delivery System catalog, Ver. 8, April 2006, the disclosure of which is incorporated herein by reference. The multi-arm polymer conjugates contain four or more polymer arms and preferably four or eight polymer arms.

For purposes of illustration and not limitation, the multi-arm polyethylene glycol (PEG) residue can be

wherein:

(x) is 0 and a positive integer, i.e. from about 0 to about 28; and

(n) is the degree of polymerization.

In one particular embodiment of the present invention, the multi-arm PEG has the structure:

wherein n is a positive integer. In one preferred embodiment of the invention, the polymers have a total molecular weight of from about 5,000 Da to about 60,000 Da, and preferably from 12,000 Da to 40,000 Da.

In yet another particular embodiment, the multi-arm PEG has the structure:

wherein n is a positive integer. In one preferred embodiment of the invention, the degree of polymerization for the multi-arm polymer (n) is from about 28 to about 350 to provide polymers having a total molecular weight of from about 5,000 Da to about 60,000 Da, and preferably from about 65 to about 270 to provide polymers having a total molecular weight of from 12,000 Da to 45,000 Da. This represents the number of repeating units in the polymer chain and is dependent on the molecular weight of the polymer.

The polymers can be converted into a suitably activated polymer, using the activation techniques described in U.S. Pat. No. 5,122,614 or 5,808,096 patents. Specifically, such PEG can be of the formula:

wherein:

(u′) is an integer from about 4 to about 455; and up to 3 terminal portions of the residue is/are capped with a methyl or other lower alkyl.

In some preferred embodiments, all four of the PEG arms can be converted to suitable activating groups, for facilitating attachment to aromatic groups. Such compounds prior to conversion include:

The polymeric substances included herein are preferably water-soluble at room temperature. A non-limiting list of such polymers include polyalkylene oxide homopolymers such as polyethylene glycol (PEG) or polypropylene glycols, polyoxyethylenated polyols, copolymers thereof and block copolymers thereof, provided that the water solubility of the block copolymers is maintained.

In a further embodiment and as an alternative to PAO-based polymers, one or more effectively non-antigenic materials such as dextran, polyvinyl alcohols, carbohydrate-based polymers, hydroxypropylmethacrylamide (HPMA), polyalkene oxides, and/or copolymers thereof can be used. See also commonly-assigned U.S. Pat. No. 6,153,655, the contents of which are incorporated herein by reference. It will be understood by those of ordinary skill that the same type of activation is employed as described herein as for PAO's such as PEG. Those of ordinary skill in the art will further realize that the foregoing list is merely illustrative and that all polymeric materials having the qualities described herein are contemplated. For purposes of the present invention, “substantially or effectively non-antigenic” means all materials understood in the art as being nontoxic and not eliciting an appreciable immunogenic response in mammals.

In some aspects, polymers having terminal amine groups can be employed to make the compounds described herein. The methods of preparing polymers containing terminal amines in high purity are described in U.S. patent application Ser. Nos. 11/508,507 and 11/537,172, the contents of each of which are incorporated by reference. For example, polymers having azides react with phosphine-based reducing agent such as triphenylphosphine or an alkali metal borohydride reducing agent such as NaBH₄. Alternatively, polymers including leaving groups react with protected amine salts such as potassium salt of methyl-tert-butyl imidodicarbonate (KNMeBoc) or the potassium salt of di-tert-butyl imidodicarbonate (KNBoc₂) followed by deprotecting the protected amine group. The purity of the polymers containing the terminal amines formed by these processes is greater than about 95% and preferably greater than 99%.

In alternative aspects, polymers having terminal carboxylic acid groups can be employed in the polymeric delivery systems described herein. Methods of preparing polymers having terminal carboxylic acids in high purity axe described in U.S. patent application Ser. No. 11/328,662, the contents of which are incorporated herein by reference. The methods include first preparing a tertiary alkyl ester of a polyalkylene oxide followed by conversion to the carboxylic acid derivative thereof. The first step of the preparation of the PAO carboxylic acids of the process includes forming an intermediate such as t-butyl ester of polyalkylene oxide carboxylic acid. This intermediate is formed by reacting a PAO with a t-butyl haloacetate in the presence of a base such as potassium t-butoxide. Once the t-butyl ester intermediate has been formed, the carboxylic acid derivative of the polyalkylene oxide can be readily provided in purities exceeding 92%, preferably exceeding 97%, more preferably exceeding 99% and most preferably exceeding 99.5% purity.

C. Hindered Esters

For purposes of the present invention, “hindered” shall be understood to mean or include a sterically crowded environment around the C(═Y₁). Such environment can be made typically by including bulk substituents, such as cyclic or branched moieties. Each of the CR₂R₃ and CR′₂R′₃ moieties adjacent to C(═Y₁) and C(═Y′₁) according to Formula (I) form hindered esters. The R₂, R′₂, R₃, R′₃ and R₅ can be selected from among hydrogen C₁₋₆ alkyl, C₂₋₆ alkenyl C₂₋₆ alkynyl, C₃₋₁₉ branched alkyl, C₃₋₈ cycloalkyl, C₁₋₆ substituted alkyl, C₂₋₆ substituted alkenyl, C₂₋₆ substituted alkynyl, C₃₋₈ substituted cycloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, C₁₋₆ heteroalkyl, substituted C₁₋₆ heteroalkyl, C₁₋₆ alkoxy, aryloxy, C₁₋₆ heteroalkoxy, heteroaryloxy, C₂₋₆ alkanoyl, arylcarbonyl, C₂₋₆ alkoxycarbonyl, aryloxycarbonyl, C₂₋₆ alkanoyloxy, arylcarbonyloxy, C₂₋₆ substituted alkanoyl, substituted arylcarbonyl, C₂₋₆ substituted alkanoyloxy, substituted aryloxycarbonyl, C₂₋₆ substituted alkanoyloxy and substituted arylcarbonyloxy. Any of the possible groups described herein for R₂ and R₃ (R′₂ and R′₃) can be used so long as both R₂ and R₃ (R′₂ and R′₃) are not simultaneously H. When one of R₂ and R₃ (R′₂ and R′₃) is H, the other contains at least three hydrocarbons.

In one preferred embodiment, R₂, R′₂, R₃ and R′₃ include methyl, ethyl and isopropyl.

In an alternative embodiment, R₂ together with R₃ and R′₂ together with R′₃ can form a substituted or unsubstituted non-aromatic cyclohydrocarbon containing at least three carbons.

D. Spacers L₁ and L′₁

In another aspect of the present invention, free electron pairs of the L₁ and L′₁ spacers linked to the CR₂R₃ and CR′₂R′₃ moieties provide enchimeric effects. Without being bound by any theory, the free electron pairs positioned four to ten atoms from C(═Y₁) and C(═Y′₁) facilitate (modify) release rate of biologically active moieties, target groups and diagnostic agents from the polymeric delivery systems described herein.

In one preferred embodiment, the L₁ and L′₁ spacers can be selected from among: —NR₁₁(CR₁₂R₁₃)_(s)—, —S(CR₁₂R₁₃)_(s)—, —O(CR₁₂R₁₃)_(s)—, —[C(═O)]_(r)(CR₁₂R₁₃)_(s)—, —NR₁₁(CR₁₂R₁₃)_(s)O(CR₁₄R₁₅)_(s′)—, —NR₁₁(CR₁₂R₁₃)_(s)S(CR₁₄R₁₅)_(s′)—, —NR₁₁(CR₁₂R₁₃)_(s)NR₁₆(CR₁₄R₁₅)_(s′)—, —NR₁₁(CR₁₂R₁₃O)_(s)(CR₁₄R₁₅)_(s′)—, —O(CR₁₂R₁₃)_(s)O(CR₁₄R₁₅)_(s′)—, —O(CR₁₂R₁₃)_(s)S(CR₁₄R₁₅)_(s′)—, —O(CR₁₂R₁₃)_(s)NR₁₆(CR₁₄R₁₅)_(s′)—, —O(CR₁₂R₁₃O)_(s)(CR₁₄R₁₅)_(s′)—,

wherein:

R₁₁-R₁₆ are independently selected from among hydrogen, amino, substituted amino, azido, carboxy, cyano, halo, hydroxyl, nitro, silyl ether, sulfonyl, mercapto, C₁₋₆ alkylmercapto, arylmercapto, substituted arylmercapto, substituted C₁₋₆ alkylthio, C₁₋₆ alkyls, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₁₉ branched alkyl, C₃₋₈ cycloalkyl, C₁₋₆ substituted alkyl, C₂₋₆ substituted alkenyl, C₂₋₆ substituted alkynyl, C₃₋₈ substituted cycloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, C₁₋₆ heteroalkyl substituted C₁₋₆ heteroalkyl, C₁₋₆ alkoxy, aryloxy, C₁₋₆ heteroalkoxy, heteroaryloxy, C₂₋₆ alkanoyl, arylcarbonyl, C₂₋₆ alkoxycarbonyl, aryloxycarbonyl, C₂₋₆ alkanoyloxy, arylcarbonyloxy, C₂₋₆ substituted alkanoyl, substituted arylcarbonyl, C₂₋₆ substituted alkanoyloxy, substituted aryloxycarbonyl, C₂₋₆ substituted alkanoyloxy, substituted and arylcarbonyloxy;

(s) and (s′) are independently zero or a positive integer; preferably from about 1 to about 4; and

(r) is 0 or 1.

Alternatively, the L₁ and L′₁, groups can be selected from among: —NH—(CH₂—CH₂O)_(p)—CH₁₂—, —C(═O)—(CH₂)_(n)—, —NH—(CH₂)_(n)—, —S—(CH₂)_(p)—, —NH—(CH₂)_(p)—O—CH₂— and —NH—C(═O)—(CH₂)_(p)—NH—C(═O)—(CH₂)_(q)—

wherein

(p) is an integer from 1 to 12; and

(n) and q are independently a positive integer, preferably from about 1 to 8, and more preferably from about 1 to 4.

In yet another preferred embodiment, the free electron pairs of the L₁₋₂ and L′₁₋₂ spacers are positioned four to eight atoms from C(═Y₁) and C(═Y′₁). More preferably, the electron pairs are positioned four to five atoms from C(═Y₁) and C(═Y′₁).

Preferred embodiments according to the preferred aspect are -L₁-C(R₂)(R₃)—C(═Y₁)— and -L′₁-C(R′₂)(R′₃)—C(═Y′₁) include:

In another aspect, the polymeric delivery systems described herein include that R₃ is a substituted or unsubstituted hydrocarbon having at least three carbons when R₂ is H, and L₁ is not the same as C(R₂)(R₃).

E. Bifunctional Linkers

The compounds described herein can include bifunctional linkers. The bifunctional lines include amino acids, amino acid derivatives, or peptides. The amino acids can be among naturally occurring and non-naturally occurring amino acids. Derivatives and analogs of the naturally occurring amino acids, as well as various art-known non-naturally occurring amino acids (D or L), hydrophobic or non-hydrophobic, are also contemplated to be within the scope of the invention. A suitable non-limiting list of the non-naturally occurring amino acids includes 2-aminoadipic acid, 3-aminoadipic acid, beta-alamine beta-aminopropionic acid, 2-aminobutyric acid, 4-aminobutyric acid, piperidinic acid, 6-aminocaproic acid, 2-aminoheptanoic acid, 2-aminoisobutyric acid, 3-aminoisobutyric acid 2-aminopimelic acid, 2,4-aminobutyric acid, desmosine, 2,2-diaminopimelic acid, 2,3-diaminopropionic acid, N-ethylglycine, N-ethylasparagine, 3-hydroxyproline, 4-hydroxyproline, isodesmosine, alloisoleucine, N-methylglycine, sarcosine, N-methyl-isoleucine, 6-N-methyl-lysine, N-methylvaline, norvaline, norleucine, and ornithine. Some preferred amino acid residues are selected from glycine, alanine, methionine and sarcosine, and more preferably, glycine.

Alternatively, L₂ and L′₂ can be selected from among: —[C(═O)]_(v)(CR₂₂R₂₃)_(t)[C(═O)]_(v′)—, —[C(═O)]_(v)(CR₂₂R₂₃)_(t)—O[C(═O)]_(v′)—, —[C(═O)]_(v)(CR₂₂R₂₃)_(t)—NR₂₆[C(═O)]_(v′)—, —[C(═O)]_(v)O(CR₂₂R₂₃)_(t)[C(═O)]_(v′)—, —[C(═O)]_(v)O(CR₂₂R₂₃)_(t)O[C(═O)]_(v′)—, —[C(═O)]_(v)O(CR₂₂R₂₃)_(t)NR₂₆[C(═O)]_(v′)—, —[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)[C(═O)]_(v′)—, —[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)O[C(═O)]_(v′)—, —[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)NR₂₆[C(═O)]_(v′)—, —[C(═O)]_(v)(CR₂₂R₂₃)_(t)O—(CR₂₈R₂₉)_(t′)[C(═O)]_(v′)—, —[C(═O)]_(v)(CR₂₂R₂₃)_(t)NR₂₆—(CR₂₈R₂₉)_(t′)[C(═O)]_(v′)—, —[C(═O)]_(v)(CR₂₂R₂₃)_(t)S—(CR₂₈R₂₉)_(t′)[C(═O)]_(v′)—, —[C(═O)]_(v)O(CR₂₂R₂₃)_(t)O—(CR₂₈R₂₉)_(t′)[C(═O)]_(v′)—, —[C(═O)]_(v)O(CR₂₂R₂₃)_(t)NR₂₆—(CR₂₈R₂₉)_(t′)[C(═O)]_(v′)—, —[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)O—(CR₂₈R₂₉)_(t′)[C(═O)]_(v′)—, —[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)NR₂₆—(CR₂₈R₂₉)_(t′)[C(═O)]_(v′)—, —[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)S—(CR₂₈R₂₉)_(t′)[C(═O)]_(v′)—, —[C(═O)]_(v)(CR₂₂R₂₃CR₂₈R₂₉O)_(t)NR₂₆[C(═O)]_(v′)—, —[C(═O)]_(v)(CR₂₂R₂₃CR₂₈R₂₉O)_(t)[C(═O)]_(v′—,) —[C(═O)]_(v)O(CR₂₂R₂₃CR₂₈R₂₉O)_(t)NR₂₆[C(═O)]_(v′)—, —[C(═O)]_(v)O(CR₂₂R₂₃CR₂₈R₂₉O)_(t)[C(═O)]_(v′)—, —[C(═O)]_(v)NR₂₁(CR₂₂R₂₃CR₂₈R₂₉O)_(t)NR₂₆[C(═O)]_(v′)—, —[C(═O)]_(v)NR₂₁(CR₂₂R₂₃CR₂₈R₂₉O)_(t)[C(═O)]_(v′)—, —[C(═O)]_(v)(CR₂₂R₂₃CR₂₈R₂₉O)_(t)(CR₂₄R₂₅)_(t′)[C(═O)]_(v′)—, —[C(═O)]_(v)O(CR₂₂R₂₃CR₂₈R₂₉O)_(t)(CR₂₄R₂₅)_(t′)[C(═O)]_(v′)—, —[C(═O)]_(v)NR₂₁(CR₂₂R₂₃CR₂₈R₂₉O)_(t)(CR₂₄R₂₅)_(t′)[C(═O)]_(v′)—, —[C(═O)]_(v)(CR₂₂R₂₃CR₂₈R₂₉O)_(t)(CR₂₄R₂₅)_(t′)O[C(═O)]_(v′)—, —[C(═O)]_(v)(CR₂₂R₂₃)_(t)(CR₂₄R₂₅CR₂₈R₂₉O)_(t′)[C(═O)]_(v′)—, —[C(═O)]_(v)(CR₂₂R₂₃)_(t)(CR₂₄R₂₅CR₂₈R₂₉O)_(t′)NR₂₆[C(═O)]_(v′)— —[C(═O)]_(v)O(CR₂₂R₂₃CR₂₈R₂₉O)_(t)(CR₂₄R₂₅)_(t′)O[C(═O)]_(v′)—, —[C(═O)]_(v)O(CR₂₂R₂₃)_(t)(CR₂₄R₂₅CR₂₈R₂₉O)_(t′)[C(═O)]_(v′)—, —[C(═O)]_(v)O(CR₂₂R₂₃)_(t)(CR₂₄CR₂₅CR₂₈R₂₉O)_(t′)NR₂₆[C(═O)]_(v′)—, —[C(═O)]_(v)NR₂₁(CR₂₂CR₂₃CR₂₈R₂₉O)_(t)(CR₂₄R₂₅)_(t′)O[C(═O)]_(v′)—, —[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)(CR₂₄R₂₅CR₂₈R₂₉O)_(t′)[C(═O)]_(v′)—, —[C(═O)]_(v)NR₂₁(CR₂₂R₂₃)_(t)(CR₂₄R₂₅CR₂₈R₂₉O)_(t′)NR₂₆[C(═O)]_(v′)—,

wherein:

R₂₁₋₂₉ are independently selected from among hydrogen, C₁₋₆ alkyls, C₃₋₁₂ branched alkyls, C₃₋₈ cycloalkyls, C₁₋₆ substituted alkyls, C₃₋₈ substituted cycloalkyls, aryls, substituted aryls, aralkyls, C₁₋₆ heteroalkyls, substituted C₁₋₆ heteroalkyls, C₁₋₆ alkoxy, phenoxy and C₁₋₆ heteroalkoxy;

(t) and (t′) are independently zero or a positive integer, preferably zero or an integer from about 1 to about 12, more preferably an integer from about 1 to about 8, and most preferably 1 or 2; and

(v) and (v′) are independently zero or 1.

In a preferred embodiment L₂ and L′₂ can be selected from among: —[C(═O)]_(r)NH(CH₂)₂CH═N—NHC(═O)—(CH₂)₂—, —[C(═O)]_(r)NH(CH₂)₂(CH₂CH₂O)₂(CH₂)₂NH[C(═O)]_(r′)—, —[C(═O)]_(r)NH(CH₂CH₂)(CH₂CH₂O)₂NH[C(═O)]_(r′)—, —[C(═O)]_(r)NH(CH₂CH₂)_(s)NH(CH₂CH₂)_(s′)[C(═O)]_(r′)—, —[C(═O)]_(r)NH(CH₂CH₂)_(s)S(CH₂CH₂)_(s′)[C(═O)]_(r′—,) —[C(═O)]_(r)NH(CH₂CH₂)(CH₂CH₂)(CH₂CH₂O)[C(═O)]_(r′)—, —[C(═O)]_(r)NH(CH₂CH₂)_(s)O(CH₂CH₂)_(s′)[C(═O)]_(r′)—, —[C(═O)]_(r)NH(CH₂CH₂O)(CH₂)NH[C(═O)]_(r′)—, —[C(═O)]_(r)NH(CH₂CH₂O)₂(CH₂)[C(═O)]_(r′)—, —[C(═O)]_(r)NH(CH₂CH₂O)_(s)(CH₂)_(s′)[C(═O)]_(r′)—, —[C(═O)]_(r)NHCH₂CH₂NH[C(═O)]_(r′—,) —[C(═O)]_(r)NH(CH₂CH₂)₂O[C(═O)]_(r′)—, —[C(═O)]_(r)NH(CH₂CH₂O)[C(═O)]_(r′)—, —[C(═O)]_(r)NH(CH₂CH₂O)₂[C(═O)]_(r′)—, —[C(═O)]_(r)NH(CH₂)₃[C(═O)]_(r′)—, —[C(═O)]_(r)O(CH₂CH₂O)₂CH₂)[C(═O)]_(r′)—, —[C(═O)]_(r)O(CH₂)₂NH(CH₂)₂[C(═O)]_(r′)—, —[C(═O)]_(r)O(CH₂CH₂O)₂NH[C(═O)]_(r′)—, —[C(═O)]_(r)O(CH₂)₂O(CH₂)₂[C(═O)]_(r′)—, —[C(═O)]_(r)O(CH₂)₂S(CH₂)₂[(═O)]_(r′)—, —[C(═O)]_(r)O(CH₂CH₂)NH[C(═O)]_(r′)—, —[C(═O)]_(r)O(CH₂CH₂)O[C(═O)]_(r′)—, —[C(═O)]_(r)O(CH₂)₃NH[C(═O)]_(r′)—, —[C(═O)]_(r)O(CH₂)₃O[C(═O)]_(r′)—, —[C(═O)]_(r)O(CH₂)₃[C(═O)]_(r′)—, —[C(═O)]_(r)CH₂NHCH₂[C(═O)]_(r′)—, —[C(═O)]_(r)CH₂OCH₂[C(═O)]_(r′)—, —[C(═O)]_(r)CH₂SCH₂[C(═O)]_(r′)—, —[C(═O)]_(r)S(CH₂)₃[C(═O)]_(r′)—, —[C(═O)]_(r)(CH₂)₃[C(═O)]_(r′)—,

wherein (r) and (r′) are independently zero or 1.

In yet another embodiment, the bifunctional linkers include:

-Val-Cit-, -Gly-Phe-Leu-Gly-, -Ala-Leu-Ala-Leu-, -Phe-Lys-,

-Val-Cit-C(═O)—CH₂OCH₂—C(═O)—, -Val-Cit-C(═O)—CH₂SCH₂—C(═O)—, and —NHCH(CH₃)—C(═O)—NH(CH₂)₆—C(CH₃)₂—C(═O)—

wherein,

Y₁₁₋₁₉ are independently O, S or NR₄;

R₃₁₋₄₈, R₅₀₋₅₁ and A₅₁ are independently selected from among hydrogen C₁₋₆ alkyls, C₃₋₁₂ branched alkyls, C₃₋₈ cycloalkyls, C₁₋₆ substituted alkyls, C₃₋₈ substituted cycloalkyls, aryls, substituted aryls, aralkyls, C₁₋₆ heteroalkyls, substituted C₁₋₆ heteroalkyls, C₁₋₆ alkoxy, phenoxy and C₁₋₆ heteroalkoxy;

Ar is an aryl or heteroaryl moiety;

L₁₁₋₁₅ are independently selected bifunctional spacers;

J and J′ are independently selected from selected from among moieties actively transported into a target cell, hydrophobic moieties, bifunctional linking moieties and combinations thereof;

(c11), (h11), (k11), (l11), (m11) and (n11) are independently selected positive integers, preferably 1;

(a11), (e11), (g11), (j11), (o11) and (q11) are independently either zero or a positive integer, preferably 1; and

(b11), (x11), (x′11), (f11), (i11) and (p11) are independently zero or one.

F. R₄ and R′₄ Groups

1. Leaving Groups

For purposes of the present invention, leaving groups are to be understood as those groups which are capable of reacting with a nucleophile found on the desired target, i.e. a biologically active moiety, a diagnostic agent, a targeting moiety, a bifunctional spacer, intermediate, etc. The targets thus contain a group for displacement, such as OH or SH groups found on proteins, peptides, enzymes, naturally or chemically synthesized therapeutic molecules such as doxorubicin, and spacers such as mono-protected diamines.

Leaving groups attached to the hindered ester allows covalent reaction to the biologically active moiety of choice, i.e. pharmaceutically active compounds (small molecular weight compounds), oligonucleotides, etc. Suitable leaving groups include; without limitations, halogen (Br, Cl), activated esters, cyclic imide thione, N-hydroxysuccinimidyl, N-hydroxyphtalimidyl, N-hydroxybenzotriazolyl, imidazole, tosylate, mesylate, tresylate, nosylate, C₁-C₆ alkyloxy, C₁-C₆ alkanoyloxy, arylcarbonyloxy, ortho-nitrophenoxy, para-nitrophenoxy, pentafluorophenoxy, 1,3,5-trichlorophenoxy, and 1,3,5-trifluorophenoxy or other suitable leaving groups as will be apparent to those of ordinary skill.

In particularly preferred embodiments of the invention, the leaving groups can be selected from among OH, methoxy, tert-butoxy, para-nitrophenoxy and N-hydroxysuccinimidyl.

2. Biologically Active Moieties

A wide variety of biologically active moieties can be attached to the activated polymers described herein. The biologically active moieties include pharmaceutically active compounds, enzymes, proteins, oligonucleotides, antibodies, monoclonal antibodies, single chain antibodies and peptides.

The biologically active moieties can include cardiovascular agents, anti-neoplastic, ant-infective, anti-fungal such as nystatin and amphotericin B, anti-anxiety agents, gastrointestinal agents, central nervous system-activating agents, analgesic, fertility agents, contraceptive agents, anti-inflammatory agents, steroidal agents, anti-urecemic agents, vasodilating agents, and vasoconstricting agents, etc.

In one aspect of the invention, the biologically active compounds are suitable for medicinal or diagnostic use in the treatment of animals, e.g., mammals, including humans, for conditions for which such treatment is desired.

In yet another aspect, hydroxyl- or thiol-containing biologically active moieties are within the scope of the present invention. The only limitations on the types of the biologically active moieties suitable for inclusion herein is that there is available at least one hydroxyl- or thiol-group which can react and link with a carrier portion and that there is not substantial loss of bioactivity in the form of conjugated to the polymeric delivery systems described herein.

Alternatively, parent compounds suitable for incorporation into the polymeric transport conjugate compounds of the invention, may be active after hydrolytic release from the linked compound, or not active after hydrolytic release but which will become active after undergoing a further chemical process/reaction. For example, an anticancer drug that is delivered to the bloodstream by the polymeric transport system, may remain inactive until entering a cancer or tumor cell, whereupon it is activated by the cancer or tumor cell chemistry, e.g., by an enzymatic reaction unique to that cell.

In one preferred embodiment the polymeric transport systems described herein include pharmaceutically active compounds.

For purposes of the present invention it shall be understood to mean that the pharmaceutically active compounds include small molecular weight molecules. Typically, pharmaceutically active compounds have a molecular weight of less than about 1,500 daltons. A non-limiting list of such compounds includes camptothecin and analogs such as SN38 or irinotecan hydroxyl- or thiol-topoisomerase I inhibitors, taxanes and paclitaxel derivatives, nucleosides including AZT and acyclovir, anthracycline compounds including daunorubicin and doxorubicin, related anti-metabolite compounds including Ara-C (cytosine arabinoside) and gemcitabine, etc.

In another preferred embodiment, the choice for conjugation is an oligonucleotide and after conjugation, the target is referred to as a residue of an oligonucleotide. The oligonucleotides can be selected from among any of the known oligonucleotides and oligodeoxynucleotides with phosphorodiester backbones or phosphorothioate backbones, locked nucleic acid (LNA), nucleic acid with peptide backbone (PNA), tricyclo-DNA, double stranded oligonucleotide (decoy ODN), catalytic RNA sequence (RNAi), ribozymes, spiegelmers, and CpG oligomers.

The “polynucleotide” (or “oligonucleotide”) of the above group of compound includes oligonucleotides and oligodeoxynucleotides, including, for example, an oligonucletide that has the same or substantially similar nucleotide sequence as does Genasense (a/k/a oblimersen sodium, produced by Genta Inc., Berkeley Heights, N.J.). Genasense is an 18-mer phosphorothioate antisense oligonucleotide, TCTCCCAGCGTGCGCCAT (SEQ ID NO: 1), that is complementary to the first six codons of the initiating sequence of the human bcl-2 mRNA (human bcl-2 mRNA is art-known, and is described, e.g., as SEQ ID NO: 19 in U.S. Pat. No. 6,414,134, incorporated by reference herein). The U.S. Food and Drug Administration (FDA) gave Genasense Orphan Drug status in August 2000.

Further, oligonucleotides and oligodeoxynucleotides useful according to the invention include, but are not limited to, the following:

Oligonucleotides and oligodeoxynucleotides with natural phosphorodiester backbone or phosphorothioate backbone or any other modified backbone analogues;

LNA (Locked Nucleic Acid);

PNA (nucleic acid with peptide backbone);

tricyclo-DNA;

decoy ODN (double stranded oligonucleotide);

catalytic R-NA sequence;

ribozymes;

spiegelmers (L-conformational oligonucleotides);

CpG oligomers, and the like, such as those disclosed at:

Tides 2002, Oligonucleotide and Peptide Technology Conferences, May 6-8, 2002, Las Vegas, Nev. and

Oligonucleotide & Peptide Technologies, 18 & 19 Nov. 2003, Hamburg, Germany, the contents of which are incorporated herein by reference.

Oligonucleotides according to the invention can also optionally include any suitable art-known nucleotide analogs and derivatives, including those listed by Table 1, below:

TABLE 1 Representative Nucleotide Analogs And Derivatives 4-acetylcytidine 5-methoxyaminomethyl-2- thiouridine 5-(carboxyhydroxymethyl)uridine beta, D-mannosylqueuosine 2′-O-methylcytidine 5-methoxycarbonylmethyl-2- thiouridine 5-carboxymethylaminomethyl-2- 5-methoxycarbonylmethyluridine thiouridine 5-carboxymethylaminomethyluridine 5-methoxyuridine Dihydrouridine 2-methylthio-N6- isopentenyladenosine 2′-O-methylpseudouridine N-((9-beta-D-ribofuranosyl-2- methylthiopurine-6-yl)carbamoyl) threonine D-galactosylqueuosine N-((9-beta-D-ribofuranosylpurine- 6-yl)N-methylcarbamoyl)threonine 2′-O-methylguanosine uridine-5-oxyacetic acid- methylester Inosine uridine-5-oxyacetic acid N6-isopentenyladenosine wybutoxosine 1-methyladenosine pseudouridine 1-methylpseudouridine queuosine 1-methylguanosine 2-thiocytidine 1-methylinosine 5-methyl-2-thiouridine 2,2-dimethylguanosine 2-thiouridine 2-methyladenosine 4-thiouridine 2-methylguanosine 5-methyluridine 3-methylcytidine N-((9-beta-D- ribofuranosylpurine-6- yl)carbamoyl)threonine 5-methylcytidine 2′-O-methyl-5-methyluridine N6-methyladenosine 2′-O-methyluridine 7-methylguanosine wybutosine 5-methylaminomethyluridine 3-(3-amino-3-carboxy-propyl) uridine Locked-adenosine Locked-cytidine Locked-guanosine Locked-thymine Locked-uridine Locked-methylcytidine

Although antisense oligonucleotides and related compounds have been mentioned as preferred targets for the attachment of the polymers containing the hindered esters, it is intended that R₄ or R′₄ include all suitable biologically active proteins, peptides, enzymes, small molecules etc. known to benefit from PEG or polymer attachment.

Modifications to the oligonucleotides contemplated in the invention include, for example, the addition to or substitution of selected nucleotides with functional groups or moieties that permit covalent linkage of an oligonucleotide to a desirable polymer, and/or the addition or substitution of functional moieties that incorporate additional charge, polarizability, hydrogen bonding, electrostatic interaction, and functionality to an oligonucleotide. Such modifications include, but are not limited to, 2′-position sugar modifications, 5-position pyrimidine modifications, 8-position purine modifications, modifications at exocyclic amines, substitution of 4-thiouridine, substitution of 5-bromo or 5-iodouracil, backbone modifications, methylations, base-pairing combinations such as the isobases isocytidine and isoguanidine, and analogous combinations. Oligonucleotide modifications can also include 3′ and 5′ modifications such as capping.

Structures of illustrative nucleoside analogs are provided below. See more examples of nucleoside analogues described in Freier & Altman; Nucl. Acid Res., 1997, 25, 4429-4443 and Uhlmann; Curr. Opinion in Drug Development, 2000, 3(2), 293-213, the contents of each of which axe incorporated herein by reference.

3. Targeting Groups

The compounds which can conjugate to the current invention described herein include targeting groups. The targeting groups include receptor ligands, an antibodies or antibody fragments, single chain antibodies, targeting peptides, targeting carbohydrate molecules or lectins. Targeting groups enhance binding or uptake of the compounds described herein a target tissue and cell population. For example, a non-limiting list of targeting groups includes vascular endothelial cell growth factor, FGF2, somatostatin and somatostatin analogs, transferrin, melanotropin, ApoE and ApoE peptides, von Willebrand's Factor and von Willebrand's Factor peptides, adenoviral fiber protein and adenoviral fiber protein peptides, PD1 and PD1 peptides, EGF and EGF peptides, RGD peptides, folate, etc.

4. Diagnostic Agents

A further aspect of the invention provides the conjugate compounds optionally prepared with a diagnostic tag linked to the polymeric delivery system described herein, wherein the tag is selected for diagnostic or imaging purposes. Thus, a suitable tag is prepared by linking any suitable moiety, e.g., an amino acid residue, to any art-standard emitting isotope, radio-opaque label, magnetic resonance label, or other non-radioactive isotopic labels suitable for magnetic resonance imaging, fluorescence-type labels, labels exhibiting visible colors and/or capable of fluorescing under ultraviolet, infrared or electrochemical stimulation, to allow for imaging tumor tissue during surgical procedures, and so forth. Optionally, the diagnostic tag is incorporated into and/or linked to a conjugated therapeutic moiety, allowing for monitoring of the distribution of a therapeutic biologically active material within an animal or human patient.

In yet a further aspect of the invention, the inventive tagged conjugates are readily prepared, by art-known methods, with any suitable label, including, e.g., radioisotope labels. Simply by way of example, these include ¹³¹Iodine, ¹²⁵Iodine, ^(99m)-Technetium and/or ¹¹¹Indium to produce radioimmunoscintigraphic agents for selective uptake into tumor cells, in vivo. For instance, there are a number of art-known methods of linking peptide to Tc-99m including, simply by way of example, those shown by U.S. Pat. Nos. 5,328,679; 5,888,474; 5,997,844; and 5,997,845, incorporated by reference herein.

G. Preferred Embodiments Corresponding to Formula

Some particular embodiments prepared by the methods described herein include:

wherein:

R₄ is selected from among OH, leaving groups, targeting groups, diagnostic agents and biologically active moieties;

(z) is a positive integer from about 1 to about 10;

(z′) is zero or a positive integer from about 1 to about 4;

mPEG has the formula: CH₃—O(CH₂CH₂O)_(n)—;

PEG has the formula —O(CH₂CH₂O)_(n)—; and

(n) is a positive integer from about 10 to about 2,300.

Preferred polymeric compounds according to the present invention include:

wherein:

drug is pharmaceutically active compounds, eyes, proteins, antibodies, monoclonal antibodies, single chain antibodies and peptides; and

all variables are previously defined.

G. Methods of Making the Activated Polymers and Conjugates Made Therewith

In one aspect of the invention, the polymeric compound having hindered ester can be prepared by conjugating a polymeric compound having a OH or a leaving group at the terminal end with a nucleophile having a protected hindered ester or a hindered acid at the distal end. Further deprotecting and activating the resulting polymeric compound will provide the compound of the current invention. The terminal group of the current invention can be either carboxylic acid form ready to be coupled with a OH or SH containing moiety or an activated form which can be replaced upon conjugating with OH or SH containing moiety.

Alternatively, a OH or SH containing compound can be conjugated to form a hindered ester intermediate, which in turn reacted with an activated polymer for the polymeric conjugate having a hindered ester with a biologically active moiety.

For purposes of illustration, the methods of preparing a hindered acyl or ester moiety-containing polymeric conjugate include:

reacting a compound of Formula (III): A₁-R₁-M₁  (III)

with a compound of Formula (IV)

under conditions sufficient to form a compound of Formula (V):

wherein:

A₁ is a capping group or M₁;

A₂ is a capping group or

M₁ is a leaving group such as halogens, activated carbonates, isocyanate, N-hydroxysuccinimidyl, tosylate, mesylate, tresylate, nosylate, ortho-nitrophenoxy, imidazole and other leaving groups known by those of ordinary skill in the art;

M₂ is —OH, —SH, or —NHR₁₀₁;

R₁₀₀ is OH or OR₁₀₁; wherein R₁₀₁ is selected from among hydrogen, C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₁₉ branched alkyl, C₃₋₈ cycloalkyl, C₁₋₆ substituted alkyl, C₂₋₆ substituted alkenyl, C₂₋₆ substituted alynyl, C₃₋₈ substituted cycloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, C₁₋₆ heteroalkyl, substituted C₁₋₆ heteroalkyl, C₁₋₆ alkoxy, aryoxy, C₁₋₆ heteroalkoxy, heteroaryloxy, C₂₋₆ alkanoyl, arylcarbonyl, C₂₋₆ alkoxycarbonyl, aryloxycarbonyl, C₂₋₆ alkanoyloxy, arylcarbonyloxy, C₂₋₆ substituted alkanoyl, substituted arylcarbonyl, C₂₋₆ substituted alkanoyloxy, substituted aryloxycarbonyl, C₂₋₆ substituted alkanoyloxy and substituted arylcarbonyloxy; and

all other variables are previously defined.

The attachment of the hindered ester moiety according to Formula (IV) to the PEG or other polymer can be done using standard chemical synthetic techniques well known to those of ordinary skill. The activated polymer portion such as SC-PEG, PEG-amine, PEG acids, etc. can be obtained from either commercial sources or synthesized by the artisan without undue experimentation.

For the purpose of the current invention, a non-limiting list of such hindered ester moiety includes:

The compounds of Formula (V) can further react with a —OH or —SH containing moiety in the presence of base and a coupling agent under conditions sufficient to form a compound of Formula (Ia):

wherein:

A₃ is a capping group or

R₁₀₃ is selected from among targeting agents, diagnostic agents and biologically active moieties; and all other variables are previously defined.

For purposes of the present invention, the R₁₀₃ is shall be understood as the portion of the OH or SH containing moiety which remains after it has undergone a reaction with the compound of Formula (V).

Alternatively, the compounds described herein can be prepared by methods including:

reacting a compound of Formula (VI):

with a compound of Formula (VII): A₄-R₁-M₄  (VII)

under conditions sufficient to form a compound of Formula (VIII):

wherein

A₄ is a capping group or M₄;

A₅ is a capping group or

M₃ is —OH, SH, or —NHR₁₀₅;

M₄ is a leaving group such as halogens, activated carbonates, isocyanate, N-hydroxysuccinimidyl, tosylate, mesylate, tresylate, nosylate, ortho-nitrophenoxy, imidazole and other leaving groups known by those of ordinary skill in the art;

R₁₀₄ is selected from biologically active moieties, targeting groups and diagnostic agents

R₁₀₅ is selected from among hydrogen, C₁₋₆ alkyl, C₂₋₄ alkenyl, C₂₋₆ alkynyl, C₃₋₁₉ branched alkyl C₃₋₈ cycloalkyl, C₁₋₆ substituted alkyl, C₂₋₆ substituted alkenyl, C₂₋₆ substituted alkynyl, C₃₋₈ substituted cycloalkyl, aryl, substituted aryl, heteroaryl substituted heteroaryl, C₁₋₆ heteroalkyl, substituted C₁₋₆ heteroalkyl, C₁₋₆ alkoxy, aryloxy, C₁₋₆ heteroalkoxy, heteroaryloxy, C₂₋₆ alkanoyl, arylcarbonyl, C₂₋₆ alkoxycarbonyl, aryloxycarbonyl, C₂₋₆ alkanoyloxy, arylcarbonyloxy, C₂₋₆ substituted alkanoyl, substituted arylcarbonyl, C₂₋₆ substituted alkanoyloxy, substituted aryloxycarbonyl, C₂₋₆ substituted alkanoyloxy and substituted arylcarbonyloxy; and

all other variables are previously defined.

Attachment of the hindered ester containing group to the polymer portion is preferably carried out in the presence of a coupling agent A non-limiting list of suitable coupling agents include 1,3-diisopropylcarbodiimide (DIPC), any suitable dialkyl carbodiimides, 2-halo-1-alkyl-pyridinium halides, (Mukaiyama reagents), 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide (EDC), propane phosphonic acid cyclic anhydride (PPACA) and phenyl dichlorophosphates, etc. which are available, for example from commercial sources such as Sigma-Aldrich Chemical, or synthesized using known techniques.

Preferably, the reactions are carried out in an inert solvent such as methylene chloride, chloroform, DMF or mixtures thereof. The reactions can be preferably conducted in the presence of a base, such as dimethylaminopyridine (DMAP), diisopropylethylamine, pyridine, triethylamine, etc. to neutralize any acids generated. The reactions can be cared out at a temperature from about 0° C. up to about 22° C. (room temperature).

H. Methods of Treatment

Another aspect of the present invention provides methods of treatment for various medical conditions in mammals. The methods include administering, to the mammal in need of such treatment, an effective amount of a compound described herein when conjugated to a biologically active moiety. The polymeric conjugate compounds are useful for, among other things, treating diseases which are similar to those which are treated with the parent compound, e.g. enzyme replacement therapy, neoplastic disease, reducing tumor burden, preventing metastasis of neoplasms and preventing recurrences of tumor/neoplastic growths in mammals.

The amount of the polymeric conjugate that is administered will depend upon the amount of the parent molecule included therein. Generally, the amount of polymeric conjugate used in the treatment methods is that amount which effectively achieves the desired therapeutic result in mammals. Naturally, the dosages of the various polymeric conjugate compounds will vary somewhat depending upon the parent compound, molecular weight of the polymer, rate of in vivo hydrolysis, etc. Those skilled in the art will determine the optimal dosing of the polymeric transport conjugates selected based on clinical experience and the treatment indication. Actual dosages will be apparent to the artisan without undue experimentation.

The compounds of the present invention can be included in one or more suitable pharmaceutical compositions for administration to mammals. The pharmaceutical compositions may be in the form of a solution, suspension, tablet, capsule or the like, prepared according to methods well known in the art. It is also contemplated that administration of such compositions may be by the oral and/or parenteral routes depending upon the needs of the artisan. A solution and/or suspension of the composition may be utilized, for example, as a carrier vehicle for injection or infiltration of the composition by any art known methods, e.g., by intravenous, intramuscular, intraperitoneal, subcutaneous injection and the like. Such administration may also be by infusion into a body space or cavity, as well as by inhalation and/or intranasal routes. In preferred aspects of the invention, however, the polymeric conjugates are parenterally administered to mammals in need thereof.

EXAMPLES

The following examples serve to provide further appreciation of the invention but are not meant in any way to restrict the scope of the invention. The bold-faced numbers recited in the Examples correspond to those shown in FIG. 1-4. Abbreviations are used throughout the examples such as, DCM (dichloromethane), DIPEA (diisopropylethylamine), DMAP (4-dimethylaminopyridine), DMF (N,N′-dimethylformamide), EDC (1-(3-dimethylaminopropyl)-3-ethyl carbodiimide), IPA (isopropanol), Mmt (4-methoxytriphenylmethyl), NHS (N-hydroxysuccinimide), PEG (polyethylene glycol), SCA-SH (single-chain antibody), SC-PEG (succinimidyl carbonate polyethylene glycol), TEAA (tetraethylammonium acetate), TFA (trifluoroacetic acid), and THF (tetrahydrofuran).

General Procedures. All reactions are run under an atmosphere of dry nitrogen or argon. Commercial reagents are used without further purification. All PEG compounds are dried under vacuum or by azeotropic distillation from toluene prior to use. ¹³C NMR spectra were obtained at 75.46 MHz using a Varian Mercury® 300 NMR spectrometer and deuterated chloroform and pyridine as the solvents unless otherwise specified Chemical shifts (δ) are reported in parts per minion (ppm) downfield from tetramethylsilane (TMS).

HPLC Method. The reaction mixtures and the purity of intermediates and final products are monitored by a Beckman Coulter System Gold® HPLC instrument. It employs a ZORBAX® 300SB C8 reversed phase column (150×4.6 mm) or a Phenomenex Jupiter® 300A C18 reversed phase column. (150×4.6 mm) with a 168 Diode Array UV Detector, using a gradient of 5-80% of acetonitrile in 0.05 M tetraethylammonium acedtate (TFAA) at a flow rate of 1 mL/min.)

Example 1 Preparation of PEG-HE-Acid, Compound (3)

SC-PEG (compound 1, Mw. 40 kDa, 1.5 g, 0.0375 mmol) was dissolved in DCM (20 mL) at room temperature. To the solution, 4-amino-2,2-dimethylbutyric acid hydrochloride (compound 2, 26.4 mg, 0.158 mmol), diisopropylethyl amine (40 μL, 0.225 mmol) and DMF (1 mL) were added. Reaction mixture was stirred for 20 hours at room temperature and solvent was partially removed in vacuo. Residue was precipitated by adding ether (40 mL) to give a white solid which was recrystallized from acetonitrile-IPA to obtain 1.35 g of product: ¹³C NMR δ 178.5, 156.5, 70.6, 63.9, 40.3, 40.2, 25.6.

Example 2 Preparation of PEG-HE-Paclitaxel, Compound (5)

Compound 3 (1.3 g, 0.0322 mmol) was dissolved in a mixture of chloroform (20 mL) and DMF (6 mL). To the stirred solution was added paclitaxel (compound 4, 0.165 g, 0.1932 mmol) followed by DMAP (51 mg, 0.420 mmol) at room temperature. The reaction mixture was then cooled at −8° C., and EDC (50 mg, 0.258 mmol) was added. The reaction mixture was allowed to warm up to room temperature and stirred for 20 hours. Solvents including DMF were removed on rotary evaporator water bath temperature not exceeding 37° C. To the remaining residue was added ether to obtain a solid which was recrystallized from acetonitrile-IPA: ¹³C NMR δ 204, 177, 174, 172, 171, 170, 167, 127-134 (7 signals), 63.8, 58.5, 55.0, 36-46 (6 signals), 9.5-28 (8 signals).

Example 3 Preparation of Br—HE-OEt, Compound (8)

Butyllithium (1.6 M solution in t-BuOH, 200 ml) was added to a solution of ethyl isobutyrate (compound 6, 35 g) in F (500 mL) at −78° C. and the solution was stirred for 1 h at the same temperature. 1,5-Dibromopetane (compound 7, 100 g) was added and the mixture was allowed to warm up to room temperature. The mire was stirred at room temperature for 1 hour and was poured into aqueous sodium bicarbonate (500 mL). The organic layer was evaporated. The residue was purified by a silica gel column, eluted with 10% ethyl acetate in hexane to give the desired product as a liquid (29.2 g, yield 36.7%).

Example 4 Preparation of N₃—HE-OEt, Compound (9)

Ethyl 7-bromo-2,2-dimethylheptanoate (compound 8, 26.5 g) was heated with sodium azide (13 g) in DMF (500 mL) at 100° C. for 2 hours. The mixture was concentrated and the residue was purified by a silica gel column, eluted with 10% ethyl acetate in hexane to give the desired product as a liquid (20.5 g, yield 90.3%).

Example 5 Preparation of N₃—HE-OH, Compound (10)

Ethyl 7-azido-2,2-dimethylheptanoate (compound 9, 20.5 g) was heated with sodium hydroxide (10 g, 85%) in ethanol (500 mL) under reflux for 2 hours. The mixture was concentrated and water (400 mL) was added. The mixture was acidified with concentrated hydrochloric acid to pH 2 and extracted with ethyl acetate (500 mL). The organic layer was concentrated and the residue was purified by a silica gel column, eluted with 50% ethyl acetate in hexane to give the desired product as a liquid (17.1 g, yield 95%).

Example 6 Preparation of N₃—HE-T, Compound (12)

7-Azido-2,2-dimethylheptanoic acid (compound 10, 8 g) was dissolved in dichloromethane (200 mL). Oxalyl chloride (6.4 g) was added and the mixture was refluxed for 2 h and evaporated. The residue was dissolved in dichloromethane (100 mL) and was added in 3′-acetyl thymidine (compound 11, 5.85 g) in pyridine (100 mL). The solution was stirred at room temperate for 24 hours and was poured into aqueous sodium bicarbonate (500 mL). The mixture was extracted with dichloromethane (500 mL) and the organic layer was concentrated. The residue was purified by a silica gel column, eluted with 5% methanol in DCM to give the desired product as a colorless solid (5.6 g, yield 61%).

Example 7 Preparation of NH₂—HE-T, Compound (13)

5′-(7-Azido-2,2-dimethylheptanoyl) 3′-acetylthymidine (compound 12, 4.65 g) was hydrogenated in methanol (200 mL) under 30 psi in the presence of Pd/C (10%, 0.5 g) for 1 h. The mixture was filtered and the filtrate was evaporated to give a solid (4.4 g, yield 100%).

Example 8 Preparation of MmtNH—HE-T, Compound (14)

5′-(7-Amino-2,2-dimethylheptanoyl) 3′-acetylthymidine (compound 13, 4.4 g), triethylamine (4 ml) and 4-methoxytrityl chloride (7.5 g) were stirred in pyridine (100 mL) for 10 h. Methylamine (40%, 10 mL) was added and the solution was stirred for 2 h. The mixture was poured into aqueous sodium bicarbonate (500 mL) and extracted with dichloromethane (500 mL). The organic layer was concentrated. The residue was purified by a silica gel column, eluted with 5% methanol in dichloromethane to give the desired product as a colorless solid (4.9 g, yield 71%).

Example 9 Preparation of MmtNH—HE-T-Phosphoroamidite, Compound (15)

5′-(7-[(MMT-amino)-2,2-dimethylheptanoyl]thymidine (Compound 14, 4.9 g), N,N-tetraisopropyl-cyanoethyl phosphoramidite (3 g) and tetrazole (0.5 g) in acetonitrile (50 ml) was stirred overnight. The mixture was poured into aqueous sodium bicarbonate (500 ml) and extracted with dichloromethane (500 ml). The organic layer was concentrated. The residue was purified by a silica gel column, eluted with 50% ethyl acetate in hexane to give the desired product as a colorless solid (4.5 g, yield 71%).

Example 10 Preparation of NH₂—HE-Oligo, Compounds (16)

Compound 15 was transferred to Trilink Biotechnologies, CA to use as the last monomer in the oligo synthesis. The Mint group was deprotected after the synthesis and the oligo was purified by RP-HPLC and compound 16 as the free anine was obtained for PEG conjugation. The sequence of oligonucleotide was TCTCCCAGCGTGCGCCAT.

Example 11 Preparation of PEG-HE-Oligo, Compounds (17)

To a solution of compound 16 (10 mg, 1.7 μmol) in PBS buffer (5 mL, pH 7.8) was added SC-PEG (compound 1, Mw 30 kDa, 520 mg, 17 μmol) and stirred at room temperature for 5 hrs. The reaction mixture was diluted to 50 mL with water and loaded on a Poros HQ, strong anion exchange column (10 mm×1.5 mm, bed volume ˜16 mL) which was pre-equilibrated with 20 mM Tris-HCl buffer, pH 7-4 (buffer A). The column was washed with 3-4 column volumes of buffer A to remove the excess PEG linker. Then the product was eluted with a gradient of 0 to 100% 1 M NaCl in 20 mM Tris-HCl buffer, pH 7.4, buffer B in 10 min, followed by 100% buffer B for 10 min at a flow rate of 10 mL/min. The eluted product was desalted using HiPrep desalting column (50 mL) and lyophilized to give 6 mg of the product. The equivalent of oligonucleotide in the conjugate measured by UV was 60%, wt/wt.

Example 12 Preparation of PEG-Linker-HE-Oligo Compound (19)

To a solution of compound 16 (10 mg, 1.7 mmol) in PBS buffer (5 mL, pH 7.8) was added PEG-Linker-NHS (compound 18, Mw 30 kDa, 520 mg, 17 μmol) and stirred at room temperature for 5 hrs. The reaction mixture was diluted to 50 mL with water and loaded on a Poros HQ, strong anion exchange column (10 mm×1.5 mm, bed volume ˜16 mL) which was pre-equilibrated with 20 mM Tris-HCl buffer, pH 74 (buffer A). The column was washed with 3-4 column volumes of buffer A to remove the excess PEG linker. Then the product was eluted with a gradient of 0 to 100% 1 M NaCl in 20 mM Tris-HCl buffer, pH 7.4, buffer B in 10 min, followed by 100% buffer B for 10 min at a flow rate of 10 mL/min. The eluted product was desalted using HiPrep desalting column (50 mL) and lyophilized to solid to give 5 mg of the desired product. The equivalent of oligonucleotide in the conjugate measured by UV was 50%, wt/wt.

Example 13 Preparation of BocNH—HE-T, Compound (22)

4-Boc-amino-2,2-dimethylbutyric acid (compound 20, 0.50 g, 2.16 mmol) was dissolved in a mire of chloroform (10 mL) and DMF (5 mL), and thymidine (compound 21, 0.79 g, 3.25 mmol) was added. The reaction mixture was cooled in an ice bath, and EDC (0.62 g, 3.25 mmol) was added, followed by DMAP (0.40 g, 3.25 mmol). The reaction mixture was allowed to warm to room temperature for 20 hours with stirring. Solvent was removed in vacuo and the residue was suspended in ethyl acetate, washed with 0.1N HCl, and brine. Organic layer was dried over anhydrous sodium sulfate and the solvent was removed in vacuo to give a crude oil. Flash column chromatography on silica gel using DCM/EtOAc (40:60, v/v) gave 0.28 g of the desired product: ¹³C NMR δ 177.21, 164.08, 156.41, 150.80, 135.46, 111.49, 85.43, 84.30, 80.21, 71.28, 63.77, 41.67, 41.08, 40.00, 37.69, 36.99, 28.87, 26.14, 25.55, 13.06.

Example 14 Preparation of NH₂—HE-T, Compounds (23)

Compound 22 (0.25 g, 0.55 mmol) was dissolved in DCM (5 mL), and TFA (0.25 mL) was added to the solution via a pipette at room temperature. The reaction mixture was stirred at room temperature for 20 minutes. Solvents and TFA were removed in vacuo by co-evaporating with DCM to remove TFA completely and to give 0.32 g of the product as a glassy solid: ¹³C NMR (CD₃CN) δ 176.61, 164.22, 150.81, 136.41, 136.18, 110.82, 85.14, 85.07, 84.14, 83.97, 70.99, 64.56, 41.32, 39.35, 37.13, 36.92, 25.10, 24.92, 24.75, 12.08, 11.98.

Example 15 Preparation of PEG-HE-T, Compounds (25)

mPEG-Linker-NHS (compound 24, Mw. 20 k, 0.50 g, 0.0246 mmol) and compound 23 (26 mg, 0.0738 mmol) were dissolved in a mixture of DCM (5 mL) and DMF (1 mL), and DMAP (15 mg, 0.0123 mmol) was added to the solution. Reaction mixture was stirred at room temperature for 2.5 hours. Solvent was removed in vacuo, and the crude product was precipitated by the addition of ethyl ether. The solid was collected by filtration and recrystallized from acetonitrile/IPA to give 0.43 g of the product as pure white solid; ¹³C NMR δ 177.9, 168.0, 164.0, 150.9, 134.9, 133.1, 129.8, 128.1, 110.2, 84.4, 83.9, 70.4, 67.8, 64.5, 63.2, 60.0, 58.7, 40.1, 39.4, 37.2, 25.2, 24.7, 16.1, 12.2.

Example 16 Preparation of PEG-HE-T, Compounds (27)

mPEG-NHS (compound 26, Mw. 20 k, 1 g, 0.0492 mmol) and compound 23 (26 mg, 0.1476 mmol) were dissolved in a of DCM (10 ml) and DMF (2 mL), and DMAP (30 mg, 0.246 mmol) was added to the solution. Reaction mixture was stirred at room temperature for 2.5 hours. Solvent was removed in vacuo, and the crude product was precipitated by the addition of ethyl ether. The solid was collected by filtration and recrystallized from acetonitrile/IPA to give 0.90 g of the product as a white sod: ¹³C NMR δ 178.2, 162.9, 156.0, 149.5, 134.6, 110.3, 84.4, 83.4, 70.1, 69.1, 64.4, 63.5, 62.6, 61.2, 58.6, 40.6, 40.0, 39.4, 37.1, 12.2.

Example 17 Determination of Stability of PEG Conjugates in Buffer and Rat Plasma

The rates of hydrolysis were obtained by employing a CS reversed phase column (Zorbax® SB-C8) using a gradient mobile phase consisting of (a) 0.1 M triethylammonium acetate buffer and (b) acetonitrile. A flow rate of 1 mL/min was used, and chromatograms were monitored using a UV detector at 227 nm for paclitaxel and 260 nm for oligonucleotides. For hydrolysis in buffer, PEG derivatives were dissolved in 0.1 M pH 7.4 PBS or water at a concentration of 5 mg/mL, while for hydrolysis in plasma, the derivatives were dissolved in distilled water at a concentration of 20 mg/100 μL and 900 μL of rat plasma was added to this solution. The mixture was vortexed for 2 min and divided into 2 mL glass vials with 100 μL of the aliquot per each vial. The solutions were incubated at 37° C. for various periods of time. A mixture of methanol-acetonitrile (1:1 v/v, 400 μL) was added to a vial at the proper interval and the mixture was vortexed for 1 min, followed by filtration through 0.45 mm filter membrane (optionally followed by a second filtration through 0.2 mm filter membrane). An aliquot of 20 μL of the filtrate was injected into the HPLC. On the basis of the peak area, the amounts of native compound and PEG derivative were estimated, and the half-life of each compound in different media was calculated using linear regression analysis from the disappearance of PEG derivative. Table below shows the result of the stability study for compounds in the examples.

TABLE Result of Stability Study of PEG conjugates Compound t_(1/2) in PBS (h) t_(1/2) in rat plasma (h) Compound 5 7.94 8.06 Compound 17 >24 >24 Compound 19 >24 16.0 

1. A compound of the Formula (I)

wherein: A is

R₁ is a polyethylene glycol; L₁ and L′₁ are each —NH(CH₂)₄—, wherein —NH is connected to L₂; L₂ and L′₂ are each —(CH₂)₂—O—C(O)—, wherein —(CH₂)₂ is connected to R₁; Y₁ and Y′₁ are independently O; R₂, R′₂, R₃, and R′₃ are independently C₁₋₆ alkyl; R₄ and R′₄ are independently biologically active moieties containing a hydroxyl moiety to form an ester; and (p) and (p′) are independently an integer from about 1 to about
 3. 2. The compound of claim 1, wherein the biologically active moiety is selected from the group consisting of pharmaceutically active compounds, enzymes, proteins, antibodies, monoclonal antibodies, single chain antibodies and peptides.
 3. The compound of claim 1, wherein -L₁-C(R₂)(R₃)—C(═Y₁)— and -L′₁—C(R′₂)(R′₃)—C(═Y′₁)— are independently


4. The compound of claim 1 having Formula (II)


5. The compound of claim 1, wherein R₁ comprises a linear, terminally branched or multi-armed polyethylene glycol.
 6. The compound of claim 5, wherein the polyethylene glycol is selected from the group consisting of —Y₇₁—(CH₂CH₂O)_(n)—CH₂CH₂Y₇₁—, —Y₇₁—(CH₂CH₂O)_(n)—CH₂C(═Y₇₂)—Y₇₁—, —Y₇₁—C(═Y₇₂)—(CH₂)_(a71)—Y₇₃—(CH₂CH₂O)_(n)—CH₂CH₂—Y₇₃—(CH₂)_(a71)—C(═Y₇₂)—Y₇₁—, and —Y₇₁—(CR₇₁R₇₂)_(a72)—Y₇₃—(CH₂)_(b71)—O—(CH₂CH₂O)_(n)—(CH₂)_(b71)—Y₇₃—(CR₇₁R₇₂)_(a72)—Y₇₁—, wherein: Y₇₁ and Y₇₃ are independently O, S, SO, SO₂, NR₇₃ or a bond; Y₇₂ is O, S, or NR₇₄; R₇₁₋₇₄ are independently the same moieties which can be used for R₂; (a71), (a72), and (b71) are independently zero or a positive integer; and (n) is an integer from about 10 to about
 2300. 7. The compound of claim 5, wherein the polyethylene glycol has the formula, —O—(CH₂CH₂O)_(n)— wherein (n) is an integer from about 10 to about 2,300.
 8. The compound of claim 1, wherein R₁ has an average molecular weight from about 2,000 to about 100,000 daltons.
 9. The compound of claim 1, wherein R₁ has an average molecular weight of from about 5,000 to about 60,000 daltons.
 10. The compound of claim 1, wherein R₁ has an average molecular weight from about 5,000 to about 25,000 daltons or from about 20,000 to about 45,000 daltons.
 11. The compound of claim 1 wherein R₂, R′₂, R₃ and R′₃ are independently selected from the group consisting of methyl, ethyl and isopropyl.
 12. A compound selected from the group consisting of:

wherein: R₄ is a biologically active moiety; (z) is a positive integer from about 1 to about 10; (z′) is zero or a positive integer from about 1 to about 4; PEG has the formula —O(CH₂CH₂O)_(n)—; and (n) is a positive integer from about 10 to about 2,300.
 13. A compound selected from the group consisting of:

wherein: drug is pharmaceutically active compounds, enzymes, proteins, antibodies, monoclonal antibodies, single chain antibodies and peptides; (z) is a positive integer from about 1 to about 10; (z′) is zero or a positive integer from about 1 to about 4; PEG has the formula —O(CH₂CH₂O)_(n)—; and (n) is a positive integer from about 10 to about 2,300. 